C Program to convert Decimal number to Octal number

In this tutorial, we will learn to write a program in c to convert a decimal number into an octal number. Here we will use the division by 8 concepts to convert it into an octal number.

Before moving towards the writing program let’s know about the Octal numbers.

What is an Octal Number?

An octal number is a number that is expressed in the base-8 numeral system. This expression contains only numbers 0 to 7. Here in the Octal system, each place is a power of 8.

For example

If we convert 108 in the octal then output will be 154.

Because in octal, the base is 8.

After calculation it will be convert into decimal like 1*8^2 + 5 * 8^1 + 4 * 8^0 = 64 + 40 + 4 = 108

By performing the calculation above we see why Octal 154 is equal to 108 in decimal.

C Program to convert decimal into octal

#include <stdio.h>
int main()
    int arr[10], num, i, j;
    printf("Program to Convert Decimal Number into Octal\n");
    printf("Please Give a Number to Convert in Octal:  ");
    scanf("%d", &num);
    printf("Octal Number of %d is =  ",num);
    for(i = 0; num > 0; i++)
        arr[i] = num % 8;
        num = num / 8;
    for(j = i - 1; j >= 0; j--)  {
        printf(" %d ", arr[j]);
    return 0;


Program to Convert Decimal Number into Octal
Please Give a Number to Convert in Octal:  34
Octal Number of 34 is =   4  2 

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